This unique field guild discusses each important aspect of the medium to high efficiency gas furnaces used in central heating applications, from the combustion process to the venting of the furnace itself. The author Richard Jazwin also provides detailed information on other related topics including: furnace construction, controls and components, ignition systems, sequences of operation, basic service procedures, and electric / electronic troubleshooting and repair. In addition to providing a basic understanding of furnace design and operation, this in depth manual also details the significant advances made in the furnace industry. "Medium and High Efficiency Gas Furnaces" is an essential tool for those who are interested in becoming successful service technicians.